The field of the subject invention includes apparatus and methods for the manufacture of railway rails, and more particularly to the hardening of high carbon steel rail by heat treatment.
The invention is particularly applicable to the hardening of rail by heat treatment through heating of the rail in a manner that achieves a balanced thermal deformation during the treatment for a rail product with a resultant straightness that considerably reduces the need for subsequent mechanical steps for distortion compensation. However, it will be appreciated to those skilled in the art that the invention could be readily adapted for use in other environments or for application to other items, for example, where similar heat treatment techniques are employed and product deformation is undesired.
Railway rail is typically comprised of high carbon steel. As trains have increased in size, power and weight, the increased loads on the rail, as well as increased traction and side thrust forces, have caused accelerated wear on the rail. The reduced life span of such rail has necessitated increased upkeep and replacement costs, more frequent inspections and substantial safety concerns.
Various forms and types of strengthened or hardened rail have been suggested and employed in the rail industry to overcome these problems, all with varying degrees of success. It has been found that the defects present in most prior proposals are such that the proposals themselves are of limited economic and practical value.
It is known to heat treat rail portions that are subject to the wear forces. Such heat treatment is applicable to high carbon or alloy steel rail. These methods suffer from the problem that metallurgical transformation, metallurgical volume changes, or thermal deformation in the rail will oftentimes require mechanical steps to compensate for the deformation of the rail. Such mechanical compensation steps are expensive and difficult to achieve, usually involve relatively large forces and limit the length of a rail that can be processed. In spite of this, subsequent straightening is required to produce an acceptable rail.
Other suggestions have comprised employing an alloy steel rail with better wear characteristics, but such a rail has the same properties throughout its volume and accordingly comprises a comparatively expensive rail. The increased expense of alloy rail has limited its applicability to situations where the cost can be justified.
Accordingly, there has been a long-felt need in the industry for improved apparatus and methods to produce railway rail having improved wear characteristics, but that can be produced at a cost below that of an alloy steel.
The present invention contemplates a new and improved apparatus and method for the hardening of high carbon steel railway rail which overcomes all of the above-referred to problems and others to provide a new method and assembly which is simple in design, economically hardens the rail where it is needed, is readily adaptable to a variety of rail dimensional characteristics and which provides a wear-resistant rail while reducing the need for subsequent mechanical steps for distortion compensation.